2293
References and Notes
Br
0 Ia
M+ Id pseudorotation
M+
Ib \
fl-G
'8
A
Br
(1) Mp 167.5-168.0°; MS Pf (a dibromo-monotin polyisotopic ion) at m/e 636 (mol wt = 638 (calcd)); tin-1 19m Mossbauer spectrum IS = 1.51 f 0.06, OS = 2.51 f 0.12 mm/sec. (2) L. M. Principe, M.A. Thesis, State University of New York at Albany, 1969; W. Z. M. Rhee. Ph.D. Thesis, State University of New York at Albany, 1974. (3) H. H. Freedman, J. Org. Chem., 27, 2298 (1962). (4) Mp 158.5-160.5' with decomposition to give a bright red liquid; IS 1.44 f 0.06, OS = 1.03 f 0.12 mm/sec. (5) A. Davison and P. Rakita. horg. Chern., 9, 289 (1970). (6) N. M. Sergeyev. G. I. Avramenko, A. V. Kisin, V. A. Korenevsky, and Yu. A. Ustynyuk, J. Organornet. Chern., 32, 55 (1971). (7) A. V. Kisin, V. A. Korenevsky, N. M. Oergeyev, and Yu. A. Ustynyuk. J. Organomet. Chern.. 34, 93 (1972). (8) Yu. K. Grishin, N. M. Sergeyev, and Yu. K. Ustynyuk, J. Organomet. Chem., 22, 361 (1970). (9) Yu. K. Grishin, N. M. Sergeyev, and Yu. A. Ustynyuk, Org. Magn. Reson., 4, 377 (1972). (10) D. L. Tomaja, Ph.D. Thesis, State University of New York at Albany, 1974. (11) Albert and Schroer, J. Organornet. Chern., 60, C6 (1973). (12) H. P. Fritz, Adv. Organornet. Chern., 1, 239 (1964). (13) The uaSym and uSym tin-cyclopentadienyl absor tions give rise to a broad, unresolved envelope in these derivatives. (14) E. W. Abel, M. 0. Dunster, and A. Waters, J. Organomet. Chem., 49, 287 (1973). (15) M. T. Rogers and J. C. Woodbury. J. Phys. Chem., 66,540 (1961). (16) F. P. Boer, J. J. Flynn, H. H. Freedman, S. V. McKinley, and V. R . Sandel, J. Am. Chem. Soc., 69,5068 (1967). (17) F. P. Boer, G. A. Doorakian, H. H. Freedman, and S.V. McKinley, J. Am. Chem. Soc.. 92, 1225 (1970). (18) F. P. Boer, F. P. vanRemoortere, P. P. North, and G. N. Reeke. Inorg. Chem., 10, 529 (1971). (19) W. L. Wells and T. L. Brown, J. Organomet. Chem., 11, 271 (1968), and references therein. (20) B. Y. K. Ho and J. J. Zuckerman, J. Organomet. Chem., 49, 1 (1973). (21) Based on these structures and hybridization arguments, the downfield resonance in the carbon-13 spectrum which has the smaller J(' 17,1'9Sn-'%) value can be assigned to the axial-cyclopentadiene group. The tin coupling in the proton spectrum is smaller for the downfield resonance only at lower temperatures. (22) Pseudorotation about either of the tin attachments to the stannole ring as a pivot would place the ring in a diequatorial position with a stannole angle C-Sn-C = 120'. Such an expansion of the ring angle at tin would be accompanied by considerable strein. (23) Square pyramidal intermediates have been proposed to rationalize the temperature-dependent proton NMR of 2-biphenylbis(4,4'-bitolyi)antimony whose singlet methyl resonance collapes to a quartet at -60' (SQ = 11.6 kcal/mol) (D. Hellwinkel and M. Bach. Naturwissenschaften, 56, 214 (1969): J. Organornet. Chern., 17, 389 (1969)). (24) Sentaphenylantimony has a square pyramidal structure in the solid: P. J. Wheatley and G. Wittlg. Roc. Chem. Soc.. London, 251 (1962): P. J. Wheatley, J. Chem. SOC., 3718 (1964); A. L. Beauchamp, M. J. Bennett, and F. A. Cotton, J. Am. Chem. Soc., 90, 6675 (1968). (25) The addition of pyridine has no effect on I.
M+ diene dissymmetry
IC
Conformers of the axially most-electronegative type (Ia) and in which the stannole ring spans one axial and one equatorial position (Ib)21 can interconvert by a pseudorotation mechanism which may go through a tetragonal pyramid (Id) as ~ h o w n . ~ IC, * - ~combining ~ both the axial-bromine and stannole ring spanning axial and equatorial positions, or the tetragonal pyramidal Id could give rise to the observed cyclopentadienyl group nonequivalence through a stannole ring nonplanarity. Such magnetic nonequivalence arising from a preferred dissymmetric diene conformation is proposed for the related (4-bromo- 1,2,3,4-tetraphenyI&,cis- 1,3-butadienyI)dimethyltin bromide, 1 6 1 8 but is less likely for I. Formulation of a lithium ion association with the stannole ring in dicyclopentadienylstannole with a bromide counterion which would rationalize the temperaturedependent spectra in terms of a dissociation of the complex is ruled out by the lack of chemical shift dependence on temperature, and by the presence of a tin-bromide shift in the infrared. Chemical shifts are sensitive to the metal ion, Li+ or TI+, however, and the lack of appreciable conductivity in nitrobenzene suggests significant ion pairing. The synthesis of I can proceed through either l-bromoI-cyclopentadienylstannole followed by adduct formation with CsHs- anion or dicyclopentadienylstannole with subsequent bromide ion uptake. The appearance of both cyclopentadienyltin resonances from the onset of reaction argues against the former. Tetraorganotin compounds show no Lewis acidity, yet the as yet unisolated 1 ,l-dicyclopentadieny1-2,3,4,5-tetraphenylstannole apparently takes up bromide ion during its formation from lithium or thallium cyclopentadiene in THF-hexane to give the [R4SnBr]- anion rather than precipitating the metal bromide.25 Acidity studies on other cyclopentadienyltin derivatives are proceeding. Acknowledgments. Our work is supported by the National Science Foundation through Grant 16,544. W e thank Drs. E. A. Williams and J. D. Cargioli of the General Electric Research and Development Center for the carbon-13 spectra, Mr. D. L. Tomaja for the tin-119m Mossbauer spectra, the M&T Chemical Co. for the generous gift of organotin starting materials, and Professors J. A. Zubieta and R. J. Zwarich for helpful discussions.
W. Z. M. Rhee, J. J. Zuckerman* Department of Chemistry State University of New York at Albany Albany, New York I2222 Received September, 16, I974
Protonated Chloromethyl Alcohol and Chloromethyl Eth'ers. Proof for the Intermediacy of the Elusive Chloromethyl Alcohol' Sir: Chloromethyl alcohol, although suggested to be an intermediate in chloromethylation with formaldehyde and hydrogen chloride,2 was not directly observed or substantiated by any evidence. Encouraged by our previous preparation and study of protonated fluoromethyl alcohol; we have extended our investigations and report now our success in directly observing (by low temperature N M R spectroscopy) protonated chloromethyl alcohol and a series of related protonated chloromethyl ethers. A clean solution of protonated chloromethyl alcohol 1 was obtained when anhydrous HCI was introduced into a Communications to the Editor
2294 Table 1.
' H NMR Data of Protonated Chloromethyl Alcohol and Chloromethyl Alkyl Ethers0 H,
Coupling constants, Hz
6.40 (t)
J , , = 4.8
11.40 (m)
6.38 (d)
4.82 (d)
J , , = 4.8 J , , = 3.3
11.00 (p)
6.40 (d)
5.37 (d,q)
11.70 (p)
6.37 (d)
5.27 (d,t)
4.16 (t)
11.17 (m)
6.37 (d)
5.21 (m)
3.90 (t)
11.83 (m)
6.43 (br s)
5.28 (m)
HZ
HI
11.67 (t)
H,
H,
H4
tir CICH,+oCl-i ?CB,
A
ClCH,+OCA,Cfi:Cl
,A
2H
ClCH,+oCA,C~,Cft,CH,+oC~~Cl
1.90 (t)
J,, J,, J,, J,, J,,
= 5.0 = 3.4 = 1.4 = 4.2 = 4.2
JIZ = 4.5 J45= 5.3
2.26 (m) 2.50 (m)
a Spectra were obtained from a Varian A56/60A spectrometer at -80" in SO,. Chemical shifts in 6 (ppm) refer to a capillary TMS and the multiplicities are given in parentheses: s, singlet; d, doublet; t , triplet; q, quartet; p, quintet; m, multiplet; br, broad.
roalkyl alcohols failed. Protonated a ~ e t a l d e h y d ewas ~ ~ unaffected by adding HC1. A series of chloromethyl alkyl ethers was also protonated in F S O ~ H - S ~ F S - S O ~solution C ~ F a t -70°, giving the corresponding chloromethyl alkyloxonium ions. IH N M R data are summarized in Table I. Protonated chloromethyl alkyl ethers are less stable than the parent, unsubstituted aliphatic ethers5 and slowly eliminate hydrogen chloride at -60' to form alkoxycarbenium ions.6 No cleavage giving protonated chloromethyl alcohol could be observed. I , , I2
, ! . , , , L . , . # , , . . I , , , / , . . , I , IO PPM,H' 8 6
,
,
,
.
H
Figure 1. 'H N M R spectrum of protonated chlorornethyl alcohol in FS03H-SbFs-SO2 solution at -80'. 4r
solution of protonated formaldehyde in FS03H-SbF5-SO2 a t -80'. The direct observation of 1 proves the intermediacy in the reaction CHzAOH
+ HC1
-
so 2
FS03H-SbF5
[ClCH,OH]
C1CH20H2'
-80
1
2
of chloromethyl alcohol 2.
FS03H- Sb F j
ClCH,OCH,CH,I
The exact nature of the reactive chloromethylating agent in electrophilic aromatic chloromethylations was never established. CH20+H and +CH*Cl are the species frequently ~ u g g e s t e d .It~ is highly improbable that the chloromethyl cation exists in any chloromethylation systems. The demonstration in the present work, that the hydroxycarbenium ion with HCl gives chloromethyl alcohol, which in acidic media is observed in its relatively stable protonated form, Le., the chloromethyloxonium ion, allows one to suggest that the latter can be a reactive intermediate in chloromethylation with formaldehyde-HC1 systems
.80°
-
H [ClCH,OCH,CH,I]
ClCH2bH2 + CH2-CH2
-80'
FS03H- SbF5
ClCH,OCH,Cl
.EO0
/'i
FS03H- SbF5
CH.0
1
H [C1CH,0CH2C1] +
2HC1
+ .R
-
ZnCIL
*
+
CICH,OHL ZnC1, R R
I
I
FSOSH-SbF5 -EOD
ClCH,OH, + (ClCH2OS02F)
The ' H N M R spectrum of 1 (Figure 1 ) shows the -+OH* triplet a t 6 11.67 ( J H - H = 4.8 Hz) and the methylene triplet a t 6 6.40. There is no evidence of exchange, including chlorine-fluorine exchange (which would show characteristic H - F coupling as found in FCH20H2+). Protonated chloromethyl alcohol is less stable than protonated fluoromethyl alcohol3 and decomposes a t temperatures above - 6 5 O . As a matter of fact its observation was unexpected and considered remarkable, because fluorine is so unique in stabilizing one carbon atom species (such as CF30F, etc.) that in no way could any analogy be expected. Attempts to prepare higher homologous protonated a-chloJournal of the American Chemical Society
+
ClCk, 'H
I
CH?CI
This suggestion is in accord with kinetic data of chloromethylations' (showing first-order dependence in aromatics and formaldehyde) and would eliminate the need to suggest either the chlorocarbenium ion (+CH2C1) or the hydroxycarbenium ion to be directly involved. In the same manner protonated (or Lewis acid complexed) chloromethyl alkyl ethers are the probable alkylating agents in chloromethylations with these ethers. W e feel that our present findings shed new light on the mechanistic aspects of chloromethylation and may also contribute to understanding the nature of the reactive alkylating species involved in the in vitro carcinogenic activity of chloromethyl ethers and related formaldehyde systems.8
/ 97:8 / April 16, 1975
2295
Acknowledgement. Support of our work by the National Science Foundation and the National Institutes of Health is gratefully acknowledged. References and Notes (1) Stable Carbocations. CXC. Part CIXC, G. A. Olah and G. Liang, J. Am. Chem. SOC.,submitted. (2) (a) G. A. Olah and W. S. Tolgyesi in "Friedel-Crafts and Related Reactions", Vol. II, Part II, G. A. Olah, Ed., Wiley-lnterscience, New York, N.Y., 1964, Chapter 21, and references given therein: (b) L. Summers, Chem. Rev., 55, 301 (1955), and references given therein: (c) R . C. Fuson and C. H. McKeever, Org. React., 1, 63 (1942), and references given. (3) G. A. Olah and Gh. D. Mateescu, J. Am. Chem. Soc., 93, 781 (1971). (4) (a) A. M. White and G. A. Olah, J. Am. Chem. SOC.,91, 2943 (1969): (b) G. A. Olah. D.H. O'Brien, and M. Calin, b i d , 89, 3582 (1967). (5) G. A. Olah and D.H. O'Brien, J. Am. Chem. SOC.,89, 1725 (1967). (6) G. A. Olah and J. M. Bollinger, J. Am. Chem. Soc., 89, 2993 (1967). (7) Y. Ogata and M. Okano, J. Am. Chem. SOC., 78, 5423 (1956). (8) (a) B. L. Van Duren et al., J. Nat. Cancer Inst., 43, 481 (1969): (b) L. Collier, Environ. Sci. Techno/.,6, 930 (1972). (9) Postdoctoral Research Fellow 1973-1974.
George A. Olah,* Simon H. Yu9 Department of Chemistry, Case Western Reserve University Cleveland, Ohio 441 06 Received January 4 , 1975
Linear Trinuclear Copper(I1)Complex with a Spin-Doublet Ground State Sir:
There have been several of oxygen-bridged trinuclear copper(I1) complexes that exhibit varying degrees of antiferromagnetic behavior. The molecular for a representative number of these complexes have revealed only two kinds of trinuclear copper clusters. Both consist of triangular arrays (I and 11) of copper ions but differ in the kind of bridging oxygen atoms (p2 or ~ 3 ) the ,
3
I
I1
I11
shape of the triangle (isosceles I or equilateral 11), and the degree of exchange coupling between copper ions. Complexes of type I exhibit subnormal room temperature magnetic moments greater than -1 BM per copper ion; that is, there is still some population of the spin 3,4 state by the three electrons of the Cu3 core a t room temperature. The magnetic behavior of type I complexes with a few exceptions has been c h a r a ~ t e r i z e d by ~ ~ assuming ~~'~ a model based upon three interacting spin l,4 species with exchange coupling between the central copper ion and its neighbors (1-2) and (1-3) but no interactions (2-3) between extreme copper ions of the triad. Complexes of type 11, however, exhibit complete spin pairing, so that only the spin-doublet state (S = ]/2) is populated at room temperature. All type I1 complexes examined to date by X-ray diffraction have shown the copper ions to be positioned a t the corners of a n equilateral triangle. W e wish to report the first example of a trinuclear copper complex having a spin-doublet ground state in which the copper ions are arranged in a strict linear fashion and joined by p2-bridging oxygen atoms, 111. The compound is the neutral copper(I1) complex of the trianion of the tetradentate ligand, IV, formed by the condensation of 2,4-pentanedione and 3-amino- 1-propanol. The compound was prepared by the reaction of copper(I1) acetylacetonate with potassium hydroxide in neat 3-amino1-propanol a t 100' over a 3-hr period. Although the initial product is contaminated with the red dimeric complex, [Cu(PIA)]211 (where PIA is the dianion of ligand V), separation was accomplished by extensive washings in hot absolute alcohol. Crystallization from a mixture of xylenes gave green needle crystals of empirical formula Cu3C22H38N404. Precession photographs (Zr-filtered Mo K a ra-
rv
ClO
Figure 1. Molecular structure of the trinuclear complex Cu3(C11H19N202)2. showing all non-hydrogen atoms. Bond distances and bond angles have deviations in the range 0.01-0.02 8, and 0.2-0.6', respectively.
Communications to the Editor
